| Message ID | pull.1848.git.git.1734488445457.gitgitgadget@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | refs: exit early from the loop if it is not a main worktree | expand |
On Wed, Dec 18, 2024 at 02:20:45AM +0000, AreaZR via GitGitGadget wrote: > From: Seija Kijin <doremylover123@gmail.com> > > The is_main_worktree function just checks for !wt->id, > but the compiler doesn't know this as it is in a different > file, so just exit out early. > I think maybe we should exit out the loop early. However, the above statement is confusing. As you have said, `is_main_worktree` checks whether the `wt->id` is NULL. Why compiler doesn't know this? And why we need to exit out the loop due to above reason? > Signed-off-by: Seija Kijin <doremylover123@gmail.com> > --- > refs: exit early from the loop if it is not a main worktree > > The is_main_worktree function just checks for !wt->id, but the compiler > doesn't know this as it is in a different file, so just exit out early. > > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1848%2FAreaZR%2Fexit-early-v1 > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1848/AreaZR/exit-early-v1 > Pull-Request: https://github.com/git/git/pull/1848 > > refs.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/refs.c b/refs.c > index 8b713692359..cce63a618d7 100644 > --- a/refs.c > +++ b/refs.c > @@ -2791,6 +2791,7 @@ static int has_worktrees(void) > if (is_main_worktree(worktrees[i])) > continue; > ret = 1; > + break; So, when we find a linked worktree, we just return the value. From my perspective, if we decide to optimize like this way, we could drop the loop because the first element of the result of `get_worktrees` is the main worktree. And we could just check whether the "worktrees[1]" is NULL to do above. However, I don't know whether it's a good idea to exit the loop early in the first place. CC Patrick to help. Thanks, Jialuo
On Wed, Dec 18, 2024 at 8:30 AM shejialuo <shejialuo@gmail.com> wrote: > On Wed, Dec 18, 2024 at 02:20:45AM +0000, AreaZR via GitGitGadget wrote: > > if (is_main_worktree(worktrees[i])) > > continue; > > ret = 1; > > + break; > > So, when we find a linked worktree, we just return the value. From my > perspective, if we decide to optimize like this way, we could drop the > loop because the first element of the result of `get_worktrees` is the > main worktree. And we could just check whether the "worktrees[1]" is > NULL to do above. You're correct. get_worktrees() guarantees that the main worktree (or bare repository) is the first item in the list, so merely checking whether `worktrees[1]` is non-NULL would be sufficient to answer whether linked worktrees are present; no looping is required. > However, I don't know whether it's a good idea to exit the loop early > in the first place. CC Patrick to help. If the loop is retained for some reason (though it really isn't needed), then exiting early is indeed desirable. I suspect that the missing `break` was just a silly oversight on Patrick's part.
Eric Sunshine <sunshine@sunshineco.com> writes: > On Wed, Dec 18, 2024 at 8:30 AM shejialuo <shejialuo@gmail.com> wrote: >> On Wed, Dec 18, 2024 at 02:20:45AM +0000, AreaZR via GitGitGadget wrote: >> > if (is_main_worktree(worktrees[i])) >> > continue; >> > ret = 1; >> > + break; >> >> So, when we find a linked worktree, we just return the value. From my >> perspective, if we decide to optimize like this way, we could drop the >> loop because the first element of the result of `get_worktrees` is the >> main worktree. And we could just check whether the "worktrees[1]" is >> NULL to do above. > > You're correct. get_worktrees() guarantees that the main worktree (or > bare repository) is the first item in the list, so merely checking > whether `worktrees[1]` is non-NULL would be sufficient to answer > whether linked worktrees are present; no looping is required. Thanks for a well-reasoned write-up. Would many other callers potentially want to know if the repository has more than one worktree? It looks to me that the has_worktrees() helper function in refs.c is a sign that the worktree API is missing a function. Calling get_worktrees() to prepare a list of worktrees and then counting the result, only to see if there are more than one, sounds a bit wasteful if we need to do so too often.
On Wed, Dec 18, 2024 at 8:10 PM Junio C Hamano <gitster@pobox.com> wrote: > Eric Sunshine <sunshine@sunshineco.com> writes: > > On Wed, Dec 18, 2024 at 8:30 AM shejialuo <shejialuo@gmail.com> wrote: > >> On Wed, Dec 18, 2024 at 02:20:45AM +0000, AreaZR via GitGitGadget wrote: > >> > if (is_main_worktree(worktrees[i])) > >> > continue; > >> > ret = 1; > >> > + break; > >> > >> So, when we find a linked worktree, we just return the value. From my > >> perspective, if we decide to optimize like this way, we could drop the > >> loop because the first element of the result of `get_worktrees` is the > >> main worktree. And we could just check whether the "worktrees[1]" is > >> NULL to do above. > > > > You're correct. get_worktrees() guarantees that the main worktree (or > > bare repository) is the first item in the list, so merely checking > > whether `worktrees[1]` is non-NULL would be sufficient to answer > > whether linked worktrees are present; no looping is required. > > Would many other callers potentially want to know if the repository > has more than one worktree? It looks to me that the has_worktrees() > helper function in refs.c is a sign that the worktree API is missing > a function. Calling get_worktrees() to prepare a list of worktrees > and then counting the result, only to see if there are more than > one, sounds a bit wasteful if we need to do so too often. If the need to answer this question does become common, then I can imagine a function being added to the worktree API which tries to be smart about it by only calling readdir() -- and validating a .git/worktrees/<id>/ metainformation -- enough times to be able to answer the question. However, although I haven't audited the code, I suspect the question "are there any linked worktrees" is rare, possibly only asked by `refs.c`. And in that case, it is asked only at the start of a refs-migration operation. Moreover, it appears that even that case of asking the question is probably temporary, existing only until someone extends the migration logic to work correctly in the presence of worktrees. (I'm sure Patrick can shed more light on this, though.)
Eric Sunshine <sunshine@sunshineco.com> writes: > However, although I haven't audited the code, I suspect the question > "are there any linked worktrees" is rare, possibly only asked by > `refs.c`. And in that case, it is asked only at the start of a > refs-migration operation. That matches my gut feeling. Thanks.
diff --git a/refs.c b/refs.c index 8b713692359..cce63a618d7 100644 --- a/refs.c +++ b/refs.c @@ -2791,6 +2791,7 @@ static int has_worktrees(void) if (is_main_worktree(worktrees[i])) continue; ret = 1; + break; } free_worktrees(worktrees);